The proposed research will develop a novel therapeutic using as proof of principle the reduction of the atherogenic risk factor, LDL. Approximately 10% of the population at risk for developing cardiovascular and peripheral vascular diseases is unable to take therapeutic doses of current lipid lowering therapies due to undesirable side effects or limited response. Clinical management of obesity and type II diabetes faces complications due to hepatosteatosis and the atherogenic risk associated with lipid mobilization from the liver into the circulation. The theoretical value of editing enzyme (APOBEC-1) gene therapy for the induction of apolipoprotein B (apoB) mRNA editing in human liver and reduction of serum LDL through the expression and secretion of apoB48-containing very low-density lipoproteins (VLDL) has long been recognized. The challenge has been how to deliver APOBEC-1 therapeutically while minimizing the risk of side effects due to unregulated enzyme activity. Controlled editing activity has been achieved in primary hepatocytes through protein transduction using TAT on APOBEC-1. A novel approach for enzyme replacement therapy has been devised involving production of APOBEC-1 chimeras in situ that are secreted from producer cells and activate apoB mRNA editing only after they transduce into neighboring hepatocytes. Secretion of APOBEC by infected hepatocytes limits its accumulation in the producing cells, eliminating the risk of off-target effects from excess editing. Chimeric APOBEC-1 constructs will be optimized in vitro for secretion-transduction and their therapeutic benefit assessed in acute animal studies. The Specific Aims are: (1) construction of a APOBEC chimera optimized for secretion, transduction and induction of activity in recipient cells;(2) transfer of the gene for the optimized TAT-APOBEC chimera into an rAAV2 vector for infection of hepatocytes in vitro and in vivo, and (3) demonstration of the secretio transduction strategy in experimental animals and its safety and affect on serum lipoproteins. Public Health Relevance: The biomedical impact of the proposed research is the development of a novel gene therapeutic approach for the safe and effective replacement of enzyme activity. The proposed research uses as proof- of-principle the induction of apolipoprotein B mRNA-editing in liver by the delivery of the enzyme APOBEC-1 in order to produce a lipid carrying protein that will reduce the atherogenic risk factor in serum known as LDL cholesterol. In addition, this therapeutic approach will satisfy the current need for interventions that can reduce fatty liver disease without resulting in elevated serum LDL and atherogenic risk.